Sadad Al-Husseini, Saudi Aramco (retired), Dhahran
Moujahed Al-Husseini, GeoArabia, Manama, Bahrain
The issue of accuracy in reporting oil and gas reserves and resources in the Middle East gulf region has been a cause for professional concern inside and outside the region for many decades.1 Hundreds of billions of barrels of oil reserves are reported as proven and undiminished, year-after-year, even though little technical data are available to confirm the reliability of these estimates.
While some producers such as Iraq and Iran have not conducted significant exploration and development programs for years to justify their current reserves, others such as Kuwait have reported conflicting proved reserves that fluctuated from 48 billion bbl to 100 billion bbl.2
To further compound these issues, unsubstantiated reports have frequently appeared in the general media that further obfuscate the accurate oil and gas resource estimates for this region. For example, on Apr. 18, 2007, the energy consultancy IHS Inc. issued a press release that stated that up to 100 billion bbl of oil resources remain to be discovered in the western desert of Iraq (www.ihs.com). Within days, this release was quoted on the front-page of London’s Financial Times followed by many other newspapers and magazines (for example: Dubai’s Gulf News, Apr. 23; Time magazine, Apr. 24; Cyprus’ MEES, Apr. 30).
Technical questions
Taking this report on its own merits, it immediately raises fundamental technical questions regarding its credibility.
First there is the reality that this conclusion stands in stark contrast to the 2004 study by the US Geological Survey (USGS) and GeoDesign, a consultancy that specializes in Iraq’s petroleum geology. The latter study estimated the undiscovered oil resources of Iraq’s western desert to total only half a billion barrels at the 95% level of probability and 1.6 billion bbl at the 50% level of probability.3
The USGS-GeoDesign study used a modern geological-statistical basin model that combined all the then-available data and knowledge regarding the petroleum reservoirs, source rocks, migration routes, and structural traps of Iraq. It considered 526 known prospects and fields, of which 370 remained undrilled, to estimate the potential number and sizes of undiscovered fields (Fig. 1).
The IHS press release stated that its own study had evaluated a comparable number of 516 known structures, of which 435 were undrilled prospects or noncommercial discoveries. From these statistics, we can conclude that both studies worked with essentially the same databases.
The USGS-GeoDesign study concluded that all the undiscovered crude oil resources of Iraq, including the western desert, may only total 13.2 billion bbl at the 95% level of probability and 45.1 billion bbl at the 50% level of probability. Even under the most optimistic circumstances at the 5% level of probability, USGS-GeoDesign did not consider the entire Iraqi undiscovered resources to exceed 84.1 billion bbl. These total estimates fall far short of the IHS conclusions for just the western desert of Iraq.
Petroleum systems
Beyond the USGS study, the conclusions of the IHS report are paradoxical because the potential petroleum resources of Iraq’s western desert are relatively easy to estimate.
For example, it is well-established from existing wells and seismic data that the prospective formations in western Iraq are mostly of Paleozoic age and are characterized by a complex lateral stratigraphy.4-9 This is confirmed by the reservoirs in Akkas field, the only commercial oil and gas-condensate field in Iraq’s western desert.
The analog to Akkas field is Jordan’s Paleozoic Risha field located along the Iraqi-Jordanian border. Risha field produces 30 MMcfd of gas from more than 30 wells. It extends across a vast area (10 by 50 km), but the reservoir is a thin sheet of complex sandstones in faulted glacio-fluvial channels, ranging in thickness from 2 to 12 m. Its proven reserves are 180 bcf of gas, the equivalent of only 32.4 million bbl of oil.
Besides Jordan and Iraq, this Paleozoic petroleum system has also been evaluated in eastern Syria and northwest Saudi Arabia by both seismic surveys and wildcat drilling. In Saudi Arabia, these efforts identified numerous exploratory prospects of considerable acreage and vertical closure comparable to other features throughout the gulf region. The oil and gas sourcing and reservoir preservation in these prospects, however, was disappointing. Only one small gas field was discovered near the northern Saudi Arabian city of Tabuk.
In contrast to these efforts, other exploration activities in Saudi Arabia and adjacent Middle East gulf countries have discovered numerous Paleozoic oil and gas fields, including the Khuff gas reservoirs, and the pre-Khuff Unayzah and Al Jawf reservoirs in Saudi Arabia.
Based on these extensive regional efforts and exploration results, the indications are clear that this vast region (extending from northwest Saudi Arabia through eastern Jordan and Syria, and western Iraq) is not very prospective for oil. In fact, to discover 100 billion bbl of crude oil in the western desert of Iraq, as suggested by the IHS report, would require discovering and delineating the equivalent of 3,000 Risha-sized oil fields. Clearly if this was a realistic possibility, many similar prospects would have been drilled and oil or gas discovered decades ago in Syria, Jordan, and northwestern Saudi Arabia.
Estimation process
Perhaps the most important conclusion to be drawn from these profoundly contradictory studies is the need for a higher level of discipline and objectivity in the process of estimating global oil reserves and resources.
After all, the difference between the two studies in this one region represents nearly 100 billion bbl of oil resources. This in turn is the equivalent of 10% of the entire world’s reported proven oil reserves.
While arriving at identical conclusions from such studies for one geological region is not realistic, discrepancies in technical estimates that differ by two orders of magnitude must surely indicate a major flaw in the resource estimation process.
References
1. Al Husseini, S.I., “The Search For Solid Ground On Oil Reserves,” Petroleum Intelligence Weekly, May 14, 2007.
2. “Reserves Issue Adds To Problems For Kuwait,” Petroleum Intelligence Weekly, May 28, 2007.
3. Verma, M.K., Ahlbrandt, T.S., and Al-Gailani, M., “Petroleum reserves and undiscovered resources in the total petroleum systems of Iraq: reserve growth and production implications,” GeoArabia, Vol. 9, 2004, No. 3.
4. Ahlbrandt, T.S., Okasheh, O.A., and Lewan, M.C., “A Middle East basin center hydrocarbon accumulation in Paleozoic Rocks, Eastern Jordan, Western Iraq and surrounding regions,” AAPG Bull., Vol. 81, 1987, pp.1,359-60.
5. Ahlbrandt, T.S., Schenk, C.J., and Pollastro, R.M., “Silurian Basin-Center Gas Petroleum Systems of the Arabian Peninsula,” abs. AAPG International Meeting, Barcelona, Spain, Sept. 21-24, 2003, p. A1.
6. Ahlbrandt, T.S., Charpentier, C.C., Klett, T.R., Schmoker, J.W., Schenk, C.J., and Ulmishek, G.E., “Global resources estimates from total petroleum systems,” AAPG Memoir 86, 2005, 324 pp.
7. Schenk, C.J., Pollastro, R.M., and Ahlbrandt, T.S., “Assessment of Undiscovered Oil and Gas of the Lower Silurian Qusaiba-Paleozoic Total Petroleum Systems of the Arabian Peninsula,” abs. AAPG International Meeting, Cairo, Egypt, Oct. 27-30, 2002, p. 77.
8. Schenk, C.J., Ahlbrandt, T.S., and Pollastro, R.M., “An Assessment of Undiscovered Oil and Gas Resources of the Greater Silurian Qusaiba-Paleozoic Total Petroleum System of the Arabian Peninsula,” abs. GeoArabia, Vol. 9, No. 1, 2004, p. 128.
9. Al-Hadidy, A.H., “Paleozoic stratigraphic lexicon and hydrocarbon habitat of Iraq,” GeoArabia, Vol. 12, No. 1, 2007, pp. 63-130.
Bibliography
Crooks, E., “Iraq’s oilfields could be twice the size-study,” Financial Times, Apr. 19, 2007.
IHS 2007 (http://www.ihs.com/News/Press-Releases/2007/IraqAtlas.htm)
Kechichian, J., “Building a wall around oil,” Gulf News, Apr. 23, 2007, p. 8.
“IHS sees possible additional 100 billion barrels oil reserves in Iraq’s Western Desert,” Middle East Economic Survey, Cyprus, Apr. 30, 2007, p. 19.
Walt, V., “Iraq Oil: More Plentiful Than Thought,” Time Magazine, Apr. 24, 2007.
The authors
Sadad Al-Husseini, formerly Saudi Aramco’s executive vice-president for exploration and producing, retired from the company on Mar. 1, 2004. He joined Saudi Aramco in 1972 and was the senior executive for exploration and development from 1986 through 2002. He has a BSc in geology American University of Beirut and an MSc and PhD in earth sciences from Brown University.
Moujahed Al-Husseini has been editor-in-chief of GeoArabia, the journal of Middle East petroleum geosciences, since 1995. He was Saudi Aramco’s exploration manager in 1989-92 when eight Paleozoic oil and gas fields were discovered in central and northwest Saudi Arabia and one in the Red Sea. He holds degrees in engineering, business, and earth sciences from King Fahd University of Petroleum and Minerals and Stanford, Brown, and Harvard universities.